Time correlations in stimulated emission
D. B. Scarl, Stephen R. Smith · Physical Review A · 1974
Measurements of two-photon coincidences in single-mode light from a He-Ne 633 nm gain tube in which each spontaneously emitted photon has an average probability of 12% of inducing a second photon, show no time correlation between inducing and induced photons in the range from zero to 3.4 nsec.